OCR Text |
Show CHAPTER IX. THE MAEKAGUNT PLATEAU. Description of its general features and relations.â€"Dog Valley.â€"One of the principal eruptive centers of trachytic masses.â€"Characters of the lavas.â€"Basaltic eruptions and conglomerates.â€"Bear Valley.â€"Little Creek Peak and Bear Peak.â€"Tufaceous beds.â€"Overlying lavas.â€"Degradation of the plateau.â€"View from the summit of Little Creek Peak.â€"Journey over the Markagunt.â€"Succession of eruptions, andesites, trachytes, rhyolites, basalts.â€"Central group of ancient basaltic cones.â€"Their dilapidated condition.â€"Panquitch Lake.â€"Exposures of contact between the lavas and sedimentaries.â€"Modern basaltic outpours.â€"Other basaltic fields.â€"Eelative recency of the basalts.â€"Surface changes since the eruptions.â€"Connection of the Markagunt basalts with those of more southern regions.â€"Sedimentary formations of the Western and Southern Markagunt.â€" Tufaceous deposits.â€"Pink Cliff beds.â€"Correlation of local Tertiaries with those of the Wasatch Plateau.â€"The Cretaceous.â€"Jurassic and Triassic formations.â€"The Shinslrump.â€"The Southern Cliffs of the Markagunt.â€"Outlook to the far southward. The Markagunt Plateau lies southwest of the Tushar. From the southern salient of Midget's Crest a considerable portion of its expanse may be seen, though the view is not a very good one. In truth there is nowhere to be obtained a good panoramic overlook of the Markagunt, for there is no stand-point sufficiently lofty. The observer on this summit, standing more than a mile above the neighboring lowlands, will find it difficult to realize that the most distant verge visible along the southwestern horizon has an altitude about equal to his own. With the exception of two respectable masses shooting up in the middle-ground of the picture, there are no peaks nor strongly individualized summits; nothing, in fact, to suggest mountains. It is a broad expanse of rolling hills and ridges, rarely exceeding 600 feet in altitude. The whole platform has a slight dip to the eastward; being, however, not an inclined plane, but dish-shaped. The eastern base of the plateau lies at the foot of the southern Sevier Plateau, being the thrown side of the great Sevier fault. From this line it rises by a very slow ascent, not exceeding 2j°, westward to its summit. The character of the gradients will be understood by a reference to the stereogram. (Atlas sheet, No. 5.) The general relations of this plateau 183 |